Beyond the Minimal Standard Model

Abstract

The GSW theory is a great step forward in our understanding of electroweak interactions because it allows the well-known extremely successful theory of quantized electrodynamics and the theory of the weak CC and NC interactions to be cast into one unified, renormalizable local gauge theory. Renormalizability, in particular, is a very desirable property of the theory because it makes covariant perturbation theory a reasonable and well-defined approximation method for calculating physical quantities beyond the lowest order diagrams. Nevertheless, this model, very likely, is not the corner stone of a final theory of weak and electromagnetic interactions. It contains very many parameters which are not predicted and whose origin remains unclear. The most prominent and specific properties of the weak interactions are built into the model (see e.g. the discussion in Sects. 3.4.1 a,b) and are not predicted. One of these is parity violation: The fact that QED conserves parity whereas (bare) CC interactions as well as neutrino induced NC interactions break parity maximally, is introduced into the theory by hand. There is not even a hint at an answer to the question of why right-handed neutrino states decouple from the physical world. Furthermore, the accuracy to which some of the empirical information on weak interactions is known, is limited, and there is indeed room for deviations from this minimal picture.